Equis ISSN 2398-2977

Keratitis: traumatic - ulcerative

Synonym(s): Corneal ulceration

Contributor(s): Paul Gerding, Nicola Menzies-Gow, Graham Munroe

Introduction

  • One of the most important ocular diseases of horses.
  • Globe is large and prominent plus the animal's normal behavior and physical activity all produce a high incidence of ulcerative keratitis in the horse.
  • Secondary infection and complication of the ulceration by bacteria and occasionally fungi can occur   Keratitis: bacterial    Keratitis: mycotic  .
  • Acute superficial traumatic ulcers usually heal quickly with minimal intervention (prophylactic topical antibiotics and mydriatic).
  • Early appropriate diagnostic methods are necessary when ulcers do not heal in 48 h, so that specific treatments related to the cause and stage of the ulcer can be initiated.
  • Frequent re-evaluations are needed until healing is obviously progressing.

Take great care to minimize the risk of globe rupture precipitated by digital pressure applied during examination of a traumatized eye. Sedation using an alpha-agonist + opiate +/- nerve blocks (auriculopalpebral or palpebral) will be required in most cases to enable a thorough examination. General anesthesia may be necessary. Avoid the use of topical local anesthetics unless indicated in order to carry out a specific procedure as they are toxic to the epithelium and will delay healing.

Print off the Owner factsheet on Common eye problems to give to your clients.

Pathophysiology

  • The majority of equine corneal ulcers result from traumatic or mechanical injury
  • Causes include:
    • Entropion   Eyelid: entropion    Eyelid: entropion 01  .
    • Cilia disorders, ectopic.
    • External eye neoplasia.
    • Exposure keratopathy   Exposure keratopathy   in association with, eg eyelid laceration   Eyelid: trauma  , ectropion   Eyelid: ectropion    Eyelid: ectropion 01  .
    • Abrasions from grazing in tall grass, fighting, head rubbing, whips, ropes, protruding objects in stables, fences, etc.
    • Foreign bodies in conjunctiva   Conjunctivitis: foreign body  and/or cornea   Cornea: foreign body    Cornea: trauma 02 - foreign body penetration      Cornea: ulcer 07 - foreign body  , especially those lodged under the third eyelid.
    • Chemical or thermal corneal injuries.
    • Corneal penetrations and/or lacerations.
  • Following initial corneal damage, a variety of factors may predispose to corneal infection and worsening of the ulceration:
    • Loss of corneal epithelium allows opportunistic bacteria and fungi to invade and adhere to corneal stroma.
    • Many equine ulcers are caused by track debris or plant material that inoculate the cornea with micro-organisms.
    • Use of topical antibiotics, particularly prolonged, alters normal bacterial and fungal flora, possibly increasing the incidence of bacterial pathogens   Eye: microbiology - overview  , and potentiating fungal growth.
    • Use of topical corticosteroids may predispose to mycotic infections   Keratitis: mycotic  .
    • Abnormality of production or distribution of tears.
    • Collagenolytic enzymatic degradation of corneal collagen (stromal 'melting')   Keratitis: bacterial    Cornea: ulcer 06 - melting  - enzyme sources include the corneal epithelium, budding endothelial cells of corneal vessels, leukocytes, especially polymorphonuclear leukocytes (PMNs), and some bacteria and fungi, especially Pseudomonas aeruginosa  Pseudomonas aeruginosa  .

Corneal repair

  • Corneal repair is unique because of its avascularity and consists of 2 processes.
  • Cell migration:
    • Epithelial cells at the wound margin lose their attachments and are able to stretch out and slide over one another to cover defect.
    • Limbal defects may encourage conjunctival epithelial cells to migrate onto the cornea.
  • Cell mitosis:
    • Mitosis of the basal layers begins at 24 h and reconstructs the epithelial thickness - completing healing in 5-7 days.
  • More severe injuries involving the corneal stroma are more complex. Involved are:
    • Stromal cellular death and edema.
    • PMN and peripheral keratocyte migration and proliferation.
    • Corneal neovascularization.
    • Production of stromal lamellae and proteoglycans often in a disorganized manner   →   corneal granulation tissue, corneal healing and remodeling and a variable amount of scarring.
  • Stromal defects can heal in 14 days.
  • Remodeling of the wound can take weeks to months.
  • Normal clarity is rarely completely restored.

Diagnosis

Clinical signs
​History
  • Duration of ulcer.
  • Prior treatment and the response to treatment.
  • Obvious predisposing condition.
  • One or both eyes affected.
  • Sudden onset, red, inflamed and painful eye.
  • Discharging eye, serous, mucous or pus.
Clinical conditions and management
  • Clinical signs and subsequent treatment of corneal ulceration are diverse and depend on the duration and severity of the problem, the presence/absence of infectious agents and which structures in the cornea and elsewhere are involved.

Superficial abrasions or erosions

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Superficial ulceration

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Chronic superficial and indolent ulceration

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Deep ulceration

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Descemetocele

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Keratomalacia ('melting ulcer')

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Further Reading

Publications

Refereed papers
  • Recent references fromPubMed andVetMedResource.
  • Hartley C (2015)Differential diagnosis and management of corneal ulceration in horses, part 2. In Pract37(1), 23-30BVA.
  • Matas Riera M & Donaldson D (2013)Case Report: Corneal graft as surgical management for deep corneal ulceration in a horse. UK Vet18, 8-10Wiley Online.
  • Utter M E & Wotman K L (2012)Distichiasis causing recurrent corneal ulceration in two Friesian horses. Equine Vet Educ24(11), 556-560VetMedResource.
  • Gilger B C (2012)The search for causes of nonhealing or recurrent ulcerative keratitis in horses. Equine Vet Educ24(11), 561-562VetMedResource.
  • Donaldson D, Matas M & Stewart J (2012)Osseous metaplasia in the conjunctiva of a horse presenting with recurrent ulcerative keratitis. Equine Vet Educ24(1), 4-7VetMedResource.
  • Utter M E, Davidson E J & Wotman K L (2009)Clinical features and outcomes of severe ulcerative keratitis with medical and surgical management in 41 horses (2000-2006). Equine Vet Educ21(6), 321-327VetMedResource
  • Galan A, Martin-Suarez E M & Gallardo J M (2009)Clinical findings and progression of 10 cases of equine ulcerative keratomycosis (2004-2007). Equine Vet Educ21(5), 236-242VetMedResource.
  • Byam-Cook K L & Knottenbelt D C (2007)Recurrent corneal ulceration secondary to an iris cyst. Equine Vet Educ19(10), 508-511VetMedResource.
  • Keller R L & Hendrix D V H (2005)Bacterial isolates and antimicrobial susceptibilities in equine bacterial ulcerative keratitis (1993-2004). Equine Vet J37(3), 207-211PubMed.
  • Krohne S G (1996)Equine ocular emergencies. Equine Pract18(2), 15-22VetMedResource.
  • Millichamp N J (1992)Ocular trauma. Vet Clin North Am Equine Pract8(3), 521-536PubMed.
  • Nasisse M P & Nelms S (1992)Equine ulcerative keratitisVet Clin North Am Equine Pract8(3), 537-555PubMed.

Other sources of information

  • Barnett K C, Crispin S M, Lavach J D & Matthews A G (2004)Equine Ophthalmology - An Atlas and Text.2nd edn. W B Saunders.
  • Brooks D E (1999)Equine Ophthalmology.3rd edn. In: Veterinary Ophthalmology.Ed: Gelatt K N. Lippincott, Williams & Wilkins. Philadelphia. pp 1053-1117.
  • Lavach J D (1990)Large Animal Ophthalmology.C V Mosby Co. St Louis, Missouri.


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